Cochlear Implant Electrode Lead and Method for Manufacturing the same

Abstract

An electrode lead for a cochlear implant system may include a tube having an interior volume and an outer peripheral surface; a plurality of stimulating electrodes disposed on a distal portion of the electrode lead; a ground electrode disposed on a proximal portion of the electrode lead for providing a current return path for stimulation current generated by the plurality of stimulation electrodes, wherein the ground electrode is ring-shaped and is fixed on and around the outer peripheral surface of the tube; and a ground wire extending within the interior volume of the tube to the ground electrode and being electrically connected to the ground electrode through an opening in a wall of the tube.

What is claimed is: 
     
         1 . An electrode lead for a cochlear implant system, comprising:
 a tube having an interior volume and an outer peripheral surface;   a plurality of stimulating electrodes disposed on a distal portion of the electrode lead;   a ground electrode disposed on a proximal portion of the electrode lead for providing a current return path for stimulation current generated by the plurality of stimulation electrodes, wherein the ground electrode is ring-shaped and is fixed on and around the outer peripheral surface of the tube;   a ground wire extending within the interior volume of the tube to the ground electrode and being electrically connected to the ground electrode through an opening in a wall of the tube;   wherein the ground electrode comprises a first end portion, a central portion axially adjacent to the first end portion, and a second end portion axially adjacent to the central portion, wherein the outer surface of the central portion is radially elevated relative to the outer surface of the first end portion and the outer surface of the second end portion, so as to form a step at a boundary between the first end portion and the central portion and at the boundary between the second end portion and the central portion, respectively.   
     
     
         2 . The electrode lead of  claim 1 , wherein an outer diameter of the central portion of the ground electrode is axially substantially constant over an entire length of the central portion so that the outer surface of the central portion is substantially cylindrical. 
     
     
         3 . The electrode lead of  claim 1 , wherein an outer diameter of the first end portion of the ground electrode is axially substantially constant over the entire length of the first end portion, and wherein the outer diameter of the second end portion of the ground electrode is axially substantially constant over the entire length of the second end portion. 
     
     
         4 . The electrode lead of  claim 1 , wherein the ground electrode comprises at least one slot for receiving an end portion of the ground wire for attachment of the ground wire to the ground electrode, and wherein the at least one slot is provided on an edge of the first end portion and/or the second end portion of the ground electrode, or wherein the at least one slot is provided in the central portion of the ground electrode. 
     
     
         5 . The electrode lead of  claim 1 , wherein the first end portion and the second end portion of the ground electrode each are covered by a silicone coating which extends from the outer surface of the tube to the step at the boundary between the central portion and the respective first end portion or the second end portion of the ground electrode so as to seal to the ground electrode to the tube. 
     
     
         6 . The electrode lead of  claim 5 , wherein the outer surface of each of the silicone coatings is substantially flush with the outer surface of the central portion of the ground electrode. 
     
     
         7 . The electrode lead of one of  claims 5 , wherein the first end portion and/or the second end portion of the ground electrode comprises at least one opening for ingress of silicone for anchoring the silicone coating to the respective first or second end portion of the ground electrode. 
     
     
         8 . The electrode lead of  claim 7 , wherein the at least one opening comprises at least one slot provided on an edge of the first end portion and/or the second end portion, or wherein the at least one opening comprises at least one hole. 
     
     
         9 . The electrode lead of  claim 5 , wherein the outer surface of the first end portion and/or the second end portion of the ground electrode is provided with surface structures, such as circumferential ribs or circumferential groves forming a partial thread, for improving adhesion of the silicone coating. 
     
     
         10 . The electrode lead of  claim 5 , wherein the outer surface of the first end portion and/or the second end portion of the ground electrode is roughened for improving adhesion of the silicone coating. 
     
     
         11 . The electrode lead of  claim 1 , wherein the tube comprises a first tube portion and a second tube portion which are axially aligned to each other and which axially abut each other, thereby forming a circumferential gap in-between which is filled with silicone and which is surrounded by the ground electrode. 
     
     
         12 . The electrode lead of  claim 11 , wherein the gap forms the opening of the tube through which the ground wire extends to the ground electrode. 
     
     
         13 . An electrode lead for a cochlear implant system, comprising:
 a tube having an interior volume and an outer peripheral surface;   a plurality of stimulating electrodes disposed on a distal portion of the electrode lead;   a ground electrode disposed on a proximal portion of the electrode lead for providing a current return path for stimulation current generated by the plurality of stimulation electrodes, wherein the ground electrode is ring-shaped and is fixed on and around the outer peripheral surface of the tube;   a ground wire extending within the interior volume of the tube to the ground electrode and being electrically connected to the ground electrode through an opening in a wall of the tube;   wherein the ground electrode comprises a first end portion, a central portion axially adjacent to the first end portion, and a second end portion axially adjacent to the central portion, and wherein each of the first end portion and the second end portion comprises a ring-like marker structure.   
     
     
         14 . A method for manufacturing an electrode lead for a cochlear implant system, comprising:
 providing a ring-shaped ground electrode having an inner surface and an outer surface and comprising a first end portion, a central portion axially adjacent to the first end portion, and a second end portion axially adjacent to the central portion;   welding an end of a ground wire to the ground electrode;   applying a silicone based adhesive to the inner surface of the ground electrode and attaching the ground electrode over an end of a first tube portion in such a manner that an end of the first tube portion extends from one side along a part of an axial length of the ground electrode into an interior of the ground electrode, wherein the ground wire extends from another side of the ground electrode;   winding a plurality of parallel electrode wires helically onto a mandrel;   inserting the mandrel with the electrode wires into the ground electrode and the first tube portion;   winding the ground wire onto the mandrel;   sliding a second tube portion onto the mandrel and into the ground electrode so that an end of the second tube portion abuts the end of the first tube portion in the interior of the ground electrode;   applying a silicone coating to the outer surface of the first and second end portion of the ground electrode and to the outer surface of the first tube portion and the second tube portion in a region adjacent to the ground electrode; and   removing the mandrel.